Zoledronic acid at subtoxic dose extends osteoblastic stage span of primary human osteoblasts

• Published in: Clinical oral investigations Vol. 19; no. 3; pp. 601 - 611
• Main Authors: Zara, Susi, De Colli, Marianna, di Giacomo, Viviana, Zizzari, Vincenzo Luca, Di Nisio, Chiara, Di Tore, Umberto, Salini, Vincenzo, Gallorini, Marialucia, Tetè, Stefano, Cataldi, Amelia
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-04-2015; Springer Nature B.V
• Subjects: Aged; Aged, 80 and over; Apoptosis - drug effects; Blotting, Western; Bone Density - drug effects; Bone Density Conservation Agents - pharmacology; Cell Differentiation - drug effects; Cell Survival - drug effects; Collagen Type I - metabolism; Dentistry; Dinoprostone - metabolism; Diphosphonates - pharmacology; Enzyme-Linked Immunosorbent Assay; Humans; Imidazoles - pharmacology; In Vitro Techniques; Interleukin-6 - metabolism; Medicine; Membrane Potential, Mitochondrial; Original Article; Osteoblasts - drug effects; Real-Time Polymerase Chain Reaction; Human osteoblasts; Collagen type I; Osteonecrosis of the jaw; Zoledronic acid; Differentiation; Apoptosis; PGE
• ISSN: 1432-6981; 1436-3771
• DOI: 10.1007/s00784-014-1280-8

Objective
This study aimed to check the effect of zoledronic acid (ZA) at subtoxic dose on human osteoblasts (HOs) in terms of cell viability, apoptosis occurrence, and differentiation induction. ZA belongs to the family of bisphosphonates (BPs), largely used in the clinical practice for the treatment of bone diseases, often associated with jaw osteonecrosis onset. Their pharmacological action consists in the direct block of the osteoclast-mediated bone resorption along with indirect action on osteoblasts.
Materials and methods
HOs were treated choosing the highest limit concentration (10
−5
 M) which does not induce toxic effects. Live/dead staining, flow cytometry, mitochondrial membrane potential assay, osteocalcin western blotting, gp38 RT-PCR, collagen type I, PGE2, and IL-6 ELISA assays were performed.
Results
Similar viability level between control and ZA-treated samples is found along with no significant increase of apoptotic and necrotic cells in ZA-treated sample. To establish if an early apoptotic pathway was triggered, Bax expression and mitochondrial membrane potential were evaluated finding a higher protein expression in control sample and a good integrity of mitochondrial membrane in both experimental points. Type I collagen secretion and alkaline phosphatase (ALP) activity appear increased in ZA-treated sample, osteocalcin expression level is reduced in ZA-treated cells, whereas no modifications of gp38 mRNA level are evidenced. No statistical differences are identified in PGE2 secretion level whereas IL-6 secretion is lower in ZA-treated HOs with respect to control ones.
Conclusions
These results highlight that ZA, delaying the osteoblastic differentiation process versus the osteocytic lineage, strengthens its pharmacological activity enhancing bone density.
Clinical relevance
The knowledge of ZA effects on osteoblasts at subtoxic dose allows to improve therapeutic protocols in order to strengthen drug pharmacological activity through a combined action on both osteoclastic and osteoblastic cells.